Ground staff are now working to replace the valve and hope to make another attempt to launch the Soyuz rocket – which is scheduled to carry two European navigation satellites into orbit – early on Friday.

"The problem was not with Soyuz, but with the ground segment of our operations," said Jean-Yves Le Gall, chairman of Arianespace, the European launch organisation that is in overall charge of operations here.

The delay is a disappointment for European and Russian space officials. The launch would have been the first of a Soyuz rocket outside the former Soviet Union and both sets of officials were hoping for an encouraging start to a new relationship between the two groups.

It has taken 350 Russian space technicians and engineers four years to build a £500m launch site for Soyuz beside Europe's launch facilities in French Guiana.

Earth's rotational speed is greatest at the equator and French Guiana lies between 2 and 4 degrees north, giving launchers an extra kick into space and reducing fuel use.

The Soyuz was scheduled to launch the first two satellites of a 30-spacecraft navigation system called Galileo, which would be a rival system to the GPS system and should free Europe from reliance on America's navigation satellites.

Le Gall said that engineers would now attempt to replace the broken valve on the ground fuel tank in time for a launch early on Friday morning, though he added that he would not be able to confirm this rescheduling until later on Thursday.